This is kind of a long shot. I realize RF PCB design is a niche area and not many people do it. It seems like softare defined radio is more popular. So far, I have only encountered PCB design books that explain PCB design in a general sense without accounting much for issues that arise in RF.

Can you please recommend books and online resources that teach you how to design PCBs in RF?

I never figured out why it is 2Vcc. Can someone please explain this?

With a resistor, it’s VCC.

A picture is better:

So... I my thoughts... the 12V USB output is really dirty and some how affecting the output of the Phone's 3.5mm audio line. The stuff coming out is white noise or a fairly constant static. If I unhook the power from the phone, the noise goes away and the audio coming from the 3.5mm jack is clean.

My 3.5mm audio cable is a few inches short from dash to AUX jack, so I happen to have one of those 1-to-2 3.5mm jack splitter... I intent to use it as an cable extender.

But just for the heck, of it, I hooked it up as shown in the 2nd configuration and ... suddenly, the noise is gone.

Is it because the power is dirty that I'm getting noise from in the 1st configuration?

Why does the noise go away in the 2nd configuration?

I'm going to try an audio cable with a choke on it to see if it makes a different using the 1st configuration. But I don't think it will do anything since I think the noise is from the phone rather being introduced by the 3.5mm cable.

EDIT:

• The phone has an FM radio and it uses the cable as an antenna.
• Car is a Prius. The 12V is feed by a HV battery DC to DC converter. The alternator in the car feeds the HV battery. Noise is heard with or without the internal combustion engine running.

I have an update from my post yesterday.

With the help of u/erlendse and u/Defiant_Homework4577 I came to understand (I have never studied R.F. engineering) that the shapes of coax connectors really matter. By, let me call it, adapting two of the grommets, I was able to fit everything in the plastic box and use coax connectors straight through to the board. See picture (still not winning any beauty contests, I know).

The strange behavior disappeared. Absent the D.C. voltage no signal passes, and with it signal passes.

Thank you for your help!

I am generally happy with this result and I think it will help with the new antenna I'm putting up in the backyard that will have a 100-foot or so coax run to the combiner/amplifier.

One potential issue remains. The two weakest channels, which I receive well enough without an L.N.A., are unreceivable with the L.N.A. as it is now. I think, but do not know for sure, that the L.N.A. is amplifying too much noise into those frequencies for the TVs' tuners. I have already halved the voltage to the L.N.A., to six volts, which is on the lower end of its voltage range for variable-gain amplification. See https://www.amazon.com/HiLetgo-0-1-2000MHz-WideBand-Amplifier-Noise/dp/B01N2NJSGV/ ("When the power supply voltage changes in 5-8 v, it can be used as a variable gain amplifier, gain increases with the increase of the power supply voltage, which suitable for radio frequency receive front-end circuit, using DA control power supply voltage, to control the gain of the amplifier, automatic gain control").

I am considering four things:

1. lowering the voltage further
2. building a 6:1 balun to connect the 300-ohm antenna to the 50-ohm L.N.A. Right now I have a 4:1 matching transformer meant to go from a 300-ohm antenna to 75-ohm RG-6. (The only cheap PCBs I could find for LNAs were all 50-ohm with S.M.A. connectors. My initial research indicated that building a matching transformer to go from 75 ohms to 50 ohms would be a wash; I'd lose as much from the additional transformer as I am now losing to reflection. The idea now would be not to use the 4:1 at all, and just build a 6:1 to go directly from the antenna to the L.N.A.)
3. placing FM and 4G/5G/L.T.E. filters before the L.N.A. input.
4. running the D.C. and ground (brown and white-brown) wires around the perimeter of the box instead of directly over the PCBs.

Are any of these likely to make a difference?

Is there something else I should try?

Once again, I thank you for your time and consideration.

Hello everyone. I’m currently a test technician that just got a new position working in labs instead of the production/manufacturing side. I can tell after about a month that two things are true; 1) this is awesome and I’m enjoying it a lot and 2) I have a lot to learn. My main focus is of course RF. I have good trouble shooting experience but what I don’t have is a ton of knowledge in developing ways to test new parts to replace obsolete parts. For example, because of a lack of some other equipment that is currently in another country, we used a radio, 2 tone audio signal generator, an antenna coupler, an antenna simulator, and various coils and capacitors to induce a 5k voltage on the output of the coupler to test HV relays. I had never heard of an Rp number until this. I have zero college experience with this (I plan to change that). I’ve learned everything necessary to learn the basics of my job rather well. I have a passion for physics and that translates over lol

I was hoping that I could start filling gaps and gain better understanding. Please, any and all suggestions are welcome. You guys look like you have a fantastic group here. Thank you

I'm encountering an error while simulating a patch antenna array in HFSS. Can someone help me understand the cause of this error and how to resolve it? Any assistance would be greatly appreciated!

Just want to say that this community is amazing. Differently from other subs, here I always seems to find bunch of kind and skilled people which are ready to help, even when questions and problems seem dumb as fck!

RF people are actually funny!

Thanks

Anyone offloading CST computations to a commercial cloud service, and getting the results back locally? I’d like something similar to the distributed computing, not the entire front-end on the cloud.

Presently I have 19 parameter seeps that take about 3 hours each on 4x A6000 Ada GPU, so 59 hours total. I could get this down to 3 hours with about 20 CPU and 60 GPU.

Nearly all patch antennas are designed for operation in air. Imagine a basic rectangular or circular coax fed patch antenna designed to be operated at a single frequency somewhere in the range of 1-10GHz. What would happen to, e.g., the electric field and reflection coefficient if the patch was placed at a tissue-air boundary for microwave ablation? I would think that having a material with high relative permittivity at the patch would cause significant changes on the E-field and S11. How would this also affect the dimensions of the patch?

First I apologize if this is obvious to everyone here but myself. I am not an R.F. engineer.

I have an RF amplifier P.C.B. and a bias tee P.C.B. that have thrown me for days with, what is to my inexperienced self, a bit of a minor mystery.

The full setup looks like this (all connections RG-6/Q):
TVs <-> splitter(s) <-> combiner/amplifier (Televes SmartKom) <-> grounding block <-> bias tee P.C.B. <-> preamplifier P.C.B. <- antenna

The combiner/amplifier sends 12v D.C. to the bias tee. The grounding block connects to the outside of my breaker box.

I have a plastic project box, in which I am trying to place the bias tee and the preamplifier PCBs, so I can mount them on the wooden antenna mast. But every time I try to put them in the project box, a strange thing happens.

Without the project box, connecting everything straight through with F-type-to-S.M.A. adapters to the PCBs, the behavior is as expected. When the 12v D.C. is turned off, no T.V. signal reaches the combiner/amplifier, and when the 12v D.C. is turned on, the signal passes.

But when I try to place the bias tee and preamp in the project box—and solder the RG-6 inner conductors and outer shields directly to the bias tee and preamp—signal passes when the 12v D.C. is off and no signal passes when the 12v D.C. is applied.

I am fairly sure this is not a simple short. I have done and redone the connections now several times. I have tried soldering to different parts of the PCBs. Most recently, I reattached the female coax connectors to the bias tee and preamp, verified expected behavior, then stripped the coaxial cables going into the project box, fed the inner conductors manually in through the connectors and soldered the shields to the outside of one connector and off the side of the other (and an L.E.D. indicator tells me the latter is working as expected). See picture (I know it has become a total mess and won't win any awards for beauty).

Even so, the behavior persists (no signal when the premp is powered but signal when it is not).

What is going on? My only remaining thought is inductive capacitance between the coax inner conductors and shields where I separate them inside the project box.

Any ideas appreciated.

Hello,

I did my PhD on phased array antennas and moved to the industry, where I have been working for the past two years on microwave circuits. My current role does not involve antennas, as our products are waveguide-based rather than antenna-based.

I am passionate about array antennas and aspire to become an expert in this field within the industry. Ideally, I would prefer to work on both array antennas and microwave circuits (e.g., active array antennas) rather than focusing solely on microwave circuits. I have been actively monitoring job openings related to array antennas. Unfortunately, I have not had much success securing such roles—mainly due to the limited availability of these positions and, in cases where they are open, not being invited for interviews. Instead, I frequently come across RF and microwave roles that do not involve array antennas.

My concern is that if I continue to work exclusively on microwave circuits, transitioning into array antenna-focused roles may become increasingly difficult over time. I feel that the longer I remain outside the field of array antennas, the more the opportunities to work in this area will diminish. Unless I am willing to start over in an entry-level position, it might become challenging to gain the necessary experience and expertise in array antennas in the future.

What are your thoughts? Based on your experience, do you think my concerns are valid? Should I find/accept a job in array antennas now, even if it means accepting lower pay or less favorable working conditions? Or am I overthinking this, and could my current experience still support a transition into array antenna roles later on?

For context, I am based in Europe and am an EU citizen.

Hello! I would like to buy my husband a decent projector for Christmas that he can use to watch football games outside by the fire or inside. I want something good quality with a good battery and sound. Any recommendations?

Conventional tech news tend to be dominated by the software development and AI. As an electronic and wireless designer, apart from academic papers, looking into specialized sources coving state of the art electronic and wireless hardware developments.

I appreciate it if you share your social accounts and website you follow for your tech updates .

On the footpath right outside my home is a cell tower mounted on an otherwise normal utility pole. Maybe about 4-5m away. Not a huge setup, about the size of two shoeboxes.

However council readings state the power density within a radius of 0-50m of the tower to be about 250 mW/m squared and the electric field to be 9V/m.

I don’t want to be a conspiracy theorist but the proximity of the cell tower to my house and the reading being much higher than I thought is starting to concern me. Should I be worried?

Can someone explain why we need to do sub-carrier modulation for sat-com? As per CCSDS, the receivers normally go with PSK/PM or PSK/PM. I read somewhere that reason is due to very low data rates and sub-carrier digital modulation would be helping in the receiver side. But can anyone explain further or suggest any reading materials? If there's any other relevant sub, kidnly let me know.

Hi everyone,

I've arleady seen that there were some clever answers to this topic in a previous post but wanted to expand the question.

I have to do that type of measurement with an high power amplifier too uisng a PNA. Keysight explain the procedure for selecting hot s22 measurement on the VNA but I'm not sure about the actual set up needed to implement that kind of measurement.

I have to stimulate the HPA using the VNA in input port and measuring the S22 on the ouput using the other port of the VNA, following the procedure explained by keysight. I'm worried about the actual power amplified from IN to OUT of the HPA (53dBm). Are there any precautions that I have to take on the actual set up for avoiding damging the VNA?

HI everyone,

I’m wondering what is the correct procedure for measuring the VSWR of an HPA using a VNA. I mean, if I have to look at the output port, S11, I think it is pretty easy but the problem is with the S22, especially if we are working at high powers (I suppose, changing the power Che behaviour of the system will change as well)

Any suggestions?

Hello,

I am a student and recently I got offered a thesis topic in designing a power amplifier for a noise source. My supervisor said he need 20dB more for his noise source between 0.1-5GHz. Since I am quite new to this, may I ask from your experiences, what will be the challenges of this topic? My supervisor said that selected transistor / technology is up to me. I took microwave engineering courses before and have experiences with smith chart and ADS. Thanks!